patch-2.4.20 linux-2.4.20/arch/x86_64/boot/compressed/head.S

• Lines: 143
• Date: Thu Nov 28 15:53:12 2002
• Orig file: linux-2.4.19/arch/x86_64/boot/compressed/head.S
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.19/arch/x86_64/boot/compressed/head.S linux-2.4.20/arch/x86_64/boot/compressed/head.S
@@ -0,0 +1,142 @@
+/*
+ *  linux/boot/head.S
+ *
+ *  Copyright (C) 1991, 1992, 1993  Linus Torvalds
+ *
+ *  $Id: head.S,v 1.3 2001/04/20 00:59:28 ak Exp $	 		
+ */
+
+/*
+ *  head.S contains the 32-bit startup code.
+ *
+ * NOTE!!! Startup happens at absolute address 0x00001000, which is also where
+ * the page directory will exist. The startup code will be overwritten by
+ * the page directory. [According to comments etc elsewhere on a compressed
+ * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]
+ *
+ * Page 0 is deliberately kept safe, since System Management Mode code in 
+ * laptops may need to access the BIOS data stored there.  This is also
+ * useful for future device drivers that either access the BIOS via VM86 
+ * mode.
+ */
+
+/*
+ * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996	
+ */
+.code32
+.text
+
+#include <linux/linkage.h>
+#include <asm/segment.h>
+
+	.code32
+	.globl startup_32
+	
+startup_32:
+	cld
+	cli
+	movl $(__KERNEL_DS),%eax
+	movl %eax,%ds
+	movl %eax,%es
+	movl %eax,%fs
+	movl %eax,%gs
+
+	lss SYMBOL_NAME(stack_start),%esp
+	xorl %eax,%eax
+1:	incl %eax		# check that A20 really IS enabled
+	movl %eax,0x000000	# loop forever if it isn't
+	cmpl %eax,0x100000
+	je 1b
+
+/*
+ * Initialize eflags.  Some BIOS's leave bits like NT set.  This would
+ * confuse the debugger if this code is traced.
+ * XXX - best to initialize before switching to protected mode.
+ */
+	pushl $0
+	popfl
+/*
+ * Clear BSS
+ */
+	xorl %eax,%eax
+	movl $ SYMBOL_NAME(_edata),%edi
+	movl $ SYMBOL_NAME(_end),%ecx
+	subl %edi,%ecx
+	cld
+	rep
+	stosb
+/*
+ * Do the decompression, and jump to the new kernel..
+ */
+	subl $16,%esp	# place for structure on the stack
+	movl %esp,%eax
+	pushl %esi	# real mode pointer as second arg
+	pushl %eax	# address of structure as first arg
+	call SYMBOL_NAME(decompress_kernel)
+	orl  %eax,%eax 
+	jnz  3f
+	addl $8,%esp
+	xorl %ebx,%ebx
+	ljmp $(__KERNEL_CS), $0x100000
+
+/*
+ * We come here, if we were loaded high.
+ * We need to move the move-in-place routine down to 0x1000
+ * and then start it with the buffer addresses in registers,
+ * which we got from the stack.
+ */
+3:
+	movl %esi,%ebx	
+	movl $move_routine_start,%esi
+	movl $0x1000,%edi
+	movl $move_routine_end,%ecx
+	subl %esi,%ecx
+	addl $3,%ecx
+	shrl $2,%ecx
+	cld
+	rep
+	movsl
+
+	popl %esi	# discard the address
+	addl $4,%esp	# real mode pointer
+	popl %esi	# low_buffer_start
+	popl %ecx	# lcount
+	popl %edx	# high_buffer_start
+	popl %eax	# hcount
+	movl $0x100000,%edi
+	cli		# make sure we don't get interrupted
+	ljmp $(__KERNEL_CS), $0x1000 # and jump to the move routine
+
+/*
+ * Routine (template) for moving the decompressed kernel in place,
+ * if we were high loaded. This _must_ PIC-code !
+ */
+move_routine_start:
+	movl %ecx,%ebp
+	shrl $2,%ecx
+	rep
+	movsl
+	movl %ebp,%ecx
+	andl $3,%ecx
+	rep
+	movsb
+	movl %edx,%esi
+	movl %eax,%ecx	# NOTE: rep movsb won't move if %ecx == 0
+	addl $3,%ecx
+	shrl $2,%ecx
+	rep
+	movsl
+	movl %ebx,%esi	# Restore setup pointer
+	xorl %ebx,%ebx
+	ljmp $(__KERNEL_CS), $0x100000
+move_routine_end:
+
+
+/* Stack for uncompression */ 	
+	.align 32
+user_stack:	 	
+	.fill 4096,4,0
+stack_start:	
+	.long user_stack+4096
+	.word __KERNEL_DS
+